ABSTRACT
A vaporiser is a device used during inhalational anaesthesia to administer a given concentration of a volatile anaesthetic agent. There are two possible paths for fresh gas to flow through the vaporiser: via the vaporising chamber itself or via the bypass pathway. Gas, which enters the vaporising chamber, becomes fully saturated with vapour. The rate of injection of desflurane must be adjusted according to the fresh gas flow otherwise turning the gas flow up would result in a dilution of the anaesthetic agent in the final gas mixture. This coupling is achieved by an electronic control unit in the vaporiser. Because of the way the vaporiser works, saturated vapour pressure (SVP) remains constant at altitude. This means the anaesthetist will have to dial in a higher percentage of desflurane to achieve the same clinical effect at altitude as at sea level.
